Error Code P06B6 is defined as Internal Control Module Knock Sensor Processor 1 Performance. This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. This includes vehicle models from but not limited to, BMW, Chevrolet, Ford, Mazda, Peugeot, Subaru, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model, and powertrain configuration.
The knock sensor is a piezoelectric sensor usually threaded straight to the engine block. Location for this sensor varies from one manufacturer to another, but it’s commonly found in the side of the block, between the water jacket freeze plugs, or in the valley underneath the intake manifold. Those knock sensors that are threaded on the side of the engine block are threaded straight into the engine coolant passages.
When the engine is warm, and the cooling system is under pressure, the removal of these sensors could lead to severe burns due to the hot coolant. Thus, it’s important to allow the engine to cool down and dispose of coolant properly when removing any of the knock sensors.
At the center of the knock sensor is the piezoelectric sensing crystal. This crystal produces a small amount of voltage when shaken or vibrated. Since the knock sensor circuit is normally a one-wire circuit, the voltage generated by the vibration is recognized by the PCM as engine noise or vibration. The severity of the vibration encountered by the crystal (inside the knock sensor) is what determines the voltage level the circuit produces.
Error Code P06B6 happens when the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has detected a performance error in the internal processor with a certain knock sensor (designated 1) circuit. Other controllers may also detect an internal PCM performance error (with the knock sensor circuit) and cause this code.
If the PCM sees a degree of knock sensor voltage that indicates an engine knock, or severe spark detonation, it may retard ignition timing, causing a knock sensor control code to be stored.
Thus, a very small amount of voltage is produced by the knock sensor when the engine is running. This is because a small amount of vibration is inevitable, no matter how smooth the engine may be running.
Internal control module monitoring processors are responsible for multiple controller self-test duties and overall internal control module accountability.
The internal control module monitoring processors oversees multiple self-test duties and overall accountability of the internal control module. Knock sensor input and output signals are subject to self-test, which are constantly monitored by the PCM and various controllers. The TCM (transmission control module), TCSM (traction control module), and other controllers interact with the knock sensor system as well.
Each time the ignition is on, the PCM is energized, resulting in the simultaneous start of the self-tests. Aside from the self-tests, the CAN (controller area network) also compares signals from each individual module, ensuring the function of each controller.
If the PCM determines any internal discrepancy in the knock sensor processors, it will store the error code and activate the malfunction light.
Additionally, if the PCM determines a problem between any of the onboard controllers, which indicates an internal knock sensor system error, this code will be stored too. For some vehicles, multiple drive cycles may be needed before the Check Engine light lights up.
- Increase in fuel consumption
- Loud noises from the engine area
- Various engine drivability problems
- Damaged or programming error in PCM
- Insufficient control module ground
- Defective knock sensor control wiring or connectors
- Defective knock sensor/s
- Blown fuse
- Bad controller power relay
- Open or shorted connectors or circuit in CAN harness
How to Check
This code is one of the tricky codes to diagnose. To make matters more difficult, it could also be a result of a reprogramming issue. Without the right reprogramming equipment, it will be impossible to replace a defective controller and complete the repair.
When diagnosing this code, it’s important to diagnose and repair other related codes first.
There are many preliminary tests before you can declare any defective controller. You’ll need a diagnostic scanner, DVOM (digital volt-ohmmeter), and a reliable vehicle information source.
Then, connect the scanner to the vehicle’s diagnostic port to retrieve all stored codes, including their freeze frame data. Take note of this information in case the problem is proven to be intermittent. Clear the codes then take the vehicle for a test drive. One of the two things can happen; either the code is restored, or the PCM enters readiness mode.
If the code enters readiness mode, then the problem is intermittent. Meaning, you would have to wait for the problem to worsen before you can accurately diagnose it. If the code is restored, however, then you can continue on your diagnosis.
Search for the TSB (technical service bulletins) that replicates the code, vehicle (year, make, model, and engine), and symptoms for the problem. You can find this information from the vehicle information source.
Then, get the face views, connector pinout charts, wiring diagrams, component locators, and diagnostic flow charts of the code for the vehicle in question.
Test the controller power supply fuses and relays using the DVOM. Replace any blown fuses, fusible links, and relays as necessary. To avoid misdiagnosis, fuses must be tested with the circuit loaded.
If fuses and relays appear to be functioning as intended, then proceed on inspecting the controller related wiring and harness (in that order). Also, make sure you check the chassis and engine ground junctions. Get the ground locations for related circuits using the vehicle information source. Then, test the ground integrity using the DVOM.
Make sure you inspect the system controllers for signs of water damage, heat, or collision damage. Any controllers with signs of damage must be considered defective and must be replaced.
If controller power and ground circuits are intact, then you can suspect a defective or programming error in the controller. This means the controller must be reprogrammed. In many cases, you can purchase reprogrammed controllers from aftermarket sources. Some vehicle/controllers require on-board reprogramming that can only be done in the dealership or another qualified source.
How to Fix
Depending on the diagnosis, common repairs for this code include:
- Repair or replacement of burnt, or damaged wirings or connectors
- Replacement of blown fuses, relays, or fusible links
- Repair of open or shorted circuit or connector in the CAN harness
- Replacement and reprogramming of PCM
This error code is categorized as severe and can result in a variety of drivability concerns.
Unlike many codes, this error code is likely caused by a defective or programming error in the controller.
Connect DVOM’s negative test lead to ground, and the positive test lead to battery voltage to test the ground integrity.